1. Field of the Invention
The present invention relates to a swashplate type variable displacement hydraulic device applied to a hydraulic pump or motor, and more particularly, to a device comprising a cylinder having a plurality of cylinder bores annularly arranged to extend in parallel with an axis of rotation and surround said axis of rotation, said cylinder being rotatable about the axis of rotation, a plurality of plungers slidably received in said cylinder bores, a swashplate having a force surface against which surface outer ends of said plungers abut, a swashplate holder adapted to support a back surface of said swashplate via bearing means, said swashplate holder being disposed to be turnable about a trunnion axis which intersects the axis of rotation at right angles, and a stationary swashplate anchor for supporting said swashplate holder.
2. Description of the Prior Art
As a hydraulic device of the aforementioned type, there is heretofore known a hydraulic device which is so constructed that a surface of a swashplate holder and a surface of a swashplate anchor located opposite to the surface of the swashplate holder are contoured in the form of a cylindrical surface, and trunnion shafts adapted to be rotatably supported by means of the swashplate anchor on an axis of the trunnion shafts are provided at both ends of the swashplate holder (for instance, see Japanese Laid-Open Patent No. 153057/1986).
With respect to the conventional hydraulic device, it has been found that a lateral pressure is developed between the swashplate holder and the swashplate anchor due to an eccentric load exerted on the swashplate via each plunger and thereby a rotational resistance of the swashplate holder increases.